ExceptionHandlingClause Class
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ExceptionHandlingClause Class

 

Represents a clause in a structured exception-handling block.

Namespace:   System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

System.Object
  System.Reflection.ExceptionHandlingClause

[ComVisibleAttribute(true)]
public class ExceptionHandlingClause

NameDescription
System_CAPS_protmethodExceptionHandlingClause()

Initializes a new instance of the ExceptionHandlingClause class.

NameDescription
System_CAPS_pubpropertyCatchType

Gets the type of exception handled by this clause.

System_CAPS_pubpropertyFilterOffset

Gets the offset within the method body, in bytes, of the user-supplied filter code.

System_CAPS_pubpropertyFlags

Gets a value indicating whether this exception-handling clause is a finally clause, a type-filtered clause, or a user-filtered clause.

System_CAPS_pubpropertyHandlerLength

Gets the length, in bytes, of the body of this exception-handling clause.

System_CAPS_pubpropertyHandlerOffset

Gets the offset within the method body, in bytes, of this exception-handling clause.

System_CAPS_pubpropertyTryLength

The total length, in bytes, of the try block that includes this exception-handling clause.

System_CAPS_pubpropertyTryOffset

The offset within the method, in bytes, of the try block that includes this exception-handling clause.

NameDescription
System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

A string representation of the exception-handling clause.(Overrides Object.ToString().)

The ExceptionHandlingClause class provides information about the clauses in a trycatchfinally block (TryCatchFinally in Visual Basic). To get a list of exception-handling clauses in a method, obtain a MethodInfo that represents the method. Use the GetMethodBody method to obtain a MethodBody object, and then use the ExceptionHandlingClauses property to get the list of clauses.

System_CAPS_noteNote

Working with exception-handling clauses requires a thorough understanding of metadata and Microsoft intermediate language (MSIL) instruction formats. Information can be found in the Common Language Infrastructure (CLI) documentation, especially "Partition II: Metadata Definition and Semantics" and "Partition III: CIL Instruction Set". The documentation is available online; see ECMA C# and Common Language Infrastructure Standards on MSDN and Standard ECMA-335 - Common Language Infrastructure (CLI) on the Ecma International Web site.

The following code example defines a test method named MethodBodyExample, and displays its local variable information and exception-handling clauses. The MethodBase.GetMethodBody method is used to obtain a MethodBody object for the test method. The ExceptionHandlingClauses property is used to obtain a list of ExceptionHandlingClause objects and display their properties.

You can use Ildasm.exe to examine the MSIL for the compiled code example, to see how the offsets and lengths are calculated.

System_CAPS_noteNote

Not all computer languages can generate ExceptionHandlingClauseOptions.Filter clauses. The Visual Basic example shows a filter clause, using a Visual Basic When expression, which is omitted from the examples for other languages.

This code is part of a larger example located in the MethodBody class topic.

using System;
using System.Reflection;

public class Example
{
    public static void Main()
    {
        // Get method body information.
        MethodInfo mi = typeof(Example).GetMethod("MethodBodyExample");
        MethodBody mb = mi.GetMethodBody();
        Console.WriteLine("\r\nMethod: {0}", mi);

        // Display the general information included in the 
        // MethodBody object.
        Console.WriteLine("    Local variables are initialized: {0}", 
            mb.InitLocals);
        Console.WriteLine("    Maximum number of items on the operand stack: {0}", 
            mb.MaxStackSize);

// Display exception handling clauses.
Console.WriteLine();
foreach (ExceptionHandlingClause ehc in mb.ExceptionHandlingClauses)
{
    Console.WriteLine(ehc.Flags.ToString());

    // The FilterOffset property is meaningful only for Filter
    // clauses. The CatchType property is not meaningful for 
    // Filter or Finally clauses. 
    switch (ehc.Flags)
    {
        case ExceptionHandlingClauseOptions.Filter:
            Console.WriteLine("        Filter Offset: {0}", 
                ehc.FilterOffset);
            break;
        case ExceptionHandlingClauseOptions.Finally:
            break;
        default:
            Console.WriteLine("    Type of exception: {0}", 
                ehc.CatchType);
            break;
    }

    Console.WriteLine("       Handler Length: {0}", ehc.HandlerLength);
    Console.WriteLine("       Handler Offset: {0}", ehc.HandlerOffset);
    Console.WriteLine("     Try Block Length: {0}", ehc.TryLength);
    Console.WriteLine("     Try Block Offset: {0}", ehc.TryOffset);
}
    }

    // The Main method contains code to analyze this method, using
    // the properties and methods of the MethodBody class.
    public void MethodBodyExample(object arg)
    {
        // Define some local variables. In addition to these variables,
        // the local variable list includes the variables scoped to 
        // the catch clauses.
        int var1 = 42;
        string var2 = "Forty-two";

        try
        {
            // Depending on the input value, throw an ArgumentException or 
            // an ArgumentNullException to test the Catch clauses.
            if (arg == null)
            {
                throw new ArgumentNullException("The argument cannot be null.");
            }
            if (arg.GetType() == typeof(string))
            {
                throw new ArgumentException("The argument cannot be a string.");
            }        
        }

        // There is no Filter clause in this code example. See the Visual 
        // Basic code for an example of a Filter clause.

        // This catch clause handles the ArgumentException class, and
        // any other class derived from Exception.
        catch(Exception ex)
        {
            Console.WriteLine("Ordinary exception-handling clause caught: {0}", 
                ex.GetType());
        }        
        finally
        {
            var1 = 3033;
            var2 = "Another string.";
        }
    }
}

// This code example produces output similar to the following:
//
//Method: Void MethodBodyExample(System.Object)
//    Local variables are initialized: True
//    Maximum number of items on the operand stack: 2
//
//Clause
//    Type of exception: System.Exception
//       Handler Length: 21
//       Handler Offset: 70
//     Try Block Length: 61
//     Try Block Offset: 9
//Finally
//       Handler Length: 14
//       Handler Offset: 94
//     Try Block Length: 85
//     Try Block Offset: 9

.NET Framework
Available since 2.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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